title: Prevalence and spectrum of electroencephalogram-identified epileptiform activity among patients with long QT syndrome.
abstract: BACKGROUND
  Congenital long QT syndrome (LQTS) is a heritable cardiac disease whereby patients are at an increased risk for LQTS-triggered syncope, seizures, and sudden cardiac arrest. Seizure episodes are common in LQTS and most often seen in patients with type 2 LQTS (LQT2).
  
  
  OBJECTIVE
  To determine the prevalence of electroencephalogram (EEG)-identified epileptiform activity among patients with LQTS.
  
  
  METHODS
  A retrospective electronic medical record review of 610 patients with LQTS (250 [41%] men), evaluated between 2000 and 2012, was performed to identify (1) all patients with LQTS who presented with seizures/seizure-like episodes, (2) patients with LQTS who underwent a subsequent neurologic evaluation and EEG study, and (3) patients with LQTS and abnormal EEG recordings that showed epileptiform activity during sinus rhythm, confirming a seizure independent from cardiac arrhythmia.
  
  
  RESULTS
  Overall, seizures/seizure-like episodes were recorded in 68 of 610 (11%) patients with LQTS. Ten patients were diagnosed with a seizure disorder by an epileptologist on the basis of the clinical findings and EEG studies, giving a prevalence of 10 of 610 (1.6%; 95% confidence interval 0.8%-3%) among patients with LQTS. A diagnosis of epilepsy was overrepresented in patients with LQT2 (7 of 190 [3.7%]) in comparison to all other LQT subgroups (3 of 420 [0.7%]; P = .0126).
  
  
  CONCLUSIONS
  While the overall prevalence of epilepsy among patients with LQTS is low, 10 of 68 (15%) of the patients who presented with seizures/seizure-like episodes had EEG-identified epileptiform activity. Confirming earlier observational reports, epilepsy is more common in patients with LQT2, further supporting the shared pathogenetic link hypothesis of this KCNH2-encoded potassium channel that is expressed in both the heart and the brain.
authors.affiliation: Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota.
authors.forename: Jason H
authors.initials: JH
authors.lastname: Anderson
authors.affiliation: Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota.
authors.forename: J Martijn
authors.initials: JM
authors.lastname: Bos
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Cascino
authors.affiliation: Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota; Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota. Electronic address: Ackerman.michael@mayo.edu.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
mesh_terms: D000328:Adult; D016757:Death, Sudden, Cardiac; D004562:Electrocardiography; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008133:Long QT Syndrome / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008910:Minnesota / Q000453:epidemiology; D015995:Prevalence; D012189:Retrospective Studies; D012640:Seizures / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology
keywords: Arrhythmia; CI; EEG; LQT1; LQT2; LQT3; LQTS; Long QT syndrome; Seizures; confidence interval; electroencephalogram; long QT syndrome; type 1 long QT syndrome; type 2 long QT syndrome; type 3 long QT syndrome